JP2002354677A - Power conditioner for solar energy generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conditioner for a solar energy generation, which can produce the maximum power from the solar cells even in an independent operation. SOLUTION: The power conditioner is composed in order to provide the output of a storage battery 21 to the input side of an inverter 13 via a bidirectional chopper 14. Accordingly, it is possible to produce the maximum power Pmax from a solar cell 20 in the same way as in a grid-connected operation. Further, the DC power from the storage battery 21 is supplied to the inverter 13 side via the bidirectional chopper 14, it is enough to control the output voltage of the bidirectional chopper 14 to a constant value of the peak value of the output voltage of the inverter 13 or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a power conditioner for photovoltaic power generation.

[0002]

2. Description of the Related Art Photovoltaic power conditioners are:
A maximum of the DC power generated by the solar cell is extracted and converted into AC power, and is connected to a power system such as a commercial power supply, so that a load (for example, a television,
This is a device for performing stable power supply to load groups such as air conditioners and refrigerators. More specifically, as shown in FIG. 2, the power conditioner 1 for photovoltaic power generation, for example, converts the output from the solar cell 2 into a predetermined DC voltage.
C / DC converter 3 and its DC / DC converter 3
And an inverter 4 for converting an output from the inverter into AC power. A load 6 connected to the power system 5 is connected to the output side of the inverter 4, and power is supplied from both the power system 5 and the inverter 4.

Here, the DC / DC converter 3 is operated at an input voltage at which the output power from the solar cell 2 is maximum (maximum power tracking control). On the other hand, since the output of the inverter 4 is connected to the power system 5, its output voltage becomes equal to the system. As a result, when the output power from the solar cell 2 is less than the power consumption in the load 6,
When the power consumption is larger than the power consumption, surplus power is supplied to the power system 5 side. Thus, stable power supply to the load 6 can be performed while extracting the maximum output from the solar cell 2.

[0004] In addition, in order to enable stable power supply to the disaster prevention load 7 and the like even in the event of a power failure, as shown in the figure, a power failure detection circuit 8 for detecting a power failure in the power system 5, a storage battery 9, A storage battery connection switch 10 that performs an opening / closing operation so as to sometimes provide an output of the storage battery 9 to an input of the DC / DC converter 3 of the power conditioner 1 is provided.
Thus, even when a power failure occurs in the power system 5 due to a disaster or the like, the solar cell 2 and the storage battery 9 can operate independently to supply power to the disaster prevention load 7.

[0005]

However, the power conditioner having the above configuration has a problem that the maximum power following control cannot be performed during the self-sustained operation, and the maximum power cannot be extracted from the solar cell 2. Was. The reason will be described with reference to a graph showing the characteristics and output relationship of the solar cell 2 shown in FIG. During the interconnection operation, the output side of the inverter 4 is connected to the power system 5 and the output voltage is equal to the voltage of the power system 5, and the input voltage of the inverter 4, that is, the output voltage of the DC / DC converter 3 is determined by the inverter 4. You. For this reason, the DC / DC converter 3 can perform the maximum power tracking control in which the input voltage is set to a voltage at which the maximum power can be extracted from the solar cell 2.

However, during the self-sustaining operation, the switch 10 for connecting the storage battery is closed, and the output side of the storage battery 9 is connected to the DC / D
Connected to the input side of C converter 3. Therefore, DC
The input side of the / DC converter 3 is governed by the output voltage Vb of the storage battery 9. This means that the output voltage Vout of the solar cell 2 connected to the input side of the DC / DC converter 3 is also governed by the voltage Vb of the storage battery. Therefore,
For example, even if the amount of solar radiation to the solar cell 2 changes and the voltage at which the maximum power can be output changes, the input voltage of the DC / DC converter 3 cannot be adjusted accordingly, and
The maximum power follow-up control becomes impossible, and the ability of the solar cell 2 cannot be fully utilized.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power conditioner for photovoltaic power generation capable of extracting maximum power from a photovoltaic cell even during independent operation.

[0008]

In order to achieve the above object, a power conditioner for photovoltaic power generation according to the invention of claim 1 operates at an input voltage at which the output power from a solar cell is maximized to reduce the voltage. A first DC / DC converter for converting, and an inverter for converting DC power from the first DC / DC converter into AC power and supplying the AC power to a load side;
A second DC / DC converter for converting DC power from a storage battery charged by a charging device to a predetermined DC voltage at an input side of the inverter and an output side of the first DC / DC converter, and outputting the converted DC voltage; It is characterized by having.

A power conditioner for photovoltaic power generation according to a second aspect of the present invention operates at an input voltage at which output power from a solar cell is maximized to convert the voltage.
A converter, an inverter that converts the DC power from the first DC / DC converter into AC power and supplies the AC power to the load side, and a DC power from the storage battery charged by the charging device on the input side of the inverter. A second DC / DC converter that converts a predetermined DC voltage to an output side of the first DC / DC converter and outputs the DC voltage, a power failure detection circuit that detects a power failure in the power system, and first and second DC / DCs Control means for controlling the converter and the inverter, wherein the control means controls the first DC / DC converter and the inverter so as to always supply power to a load connected to the power system while being connected to the power system. With the second DC / DC
An interconnection operation for stopping the converter is performed, and when a power failure detection signal that detects a power failure of the power system is received from the power failure detection circuit, both DC / DC converters and the inverter are operated to output the second DC / DC converter. The feature is that control is performed so that an input voltage required for the inverter is obtained.

[0010]

According to the first aspect of the present invention, the output from the storage battery is not supplied to the input side of the first DC / DC converter connected to the solar cell, but to the second D / D converter.
Since the power is supplied to the input side of the inverter via the C / DC converter, the input voltage of the first DC / DC converter is not influenced by the output voltage of the storage battery as in the conventional power conditioner. Therefore, the first D
The C / DC converter can be operated by the maximum power tracking control with the input voltage at which the maximum power can always be extracted from the solar cell, and the power generation capacity of the solar cell can be used efficiently. In addition, the DC power from the storage battery is converted into a predetermined DC voltage via the second DC / DC converter and supplied to the input side of the inverter.

<Invention of Claim 2> According to the invention of claim 2, when the solar cell is operated in cooperation with the power system, the second
The DC / DC converter is stopped and operated similarly to the conventional power conditioner for photovoltaic power generation.
That is, the first DC / DC converter is controlled to follow the maximum power so that the output power from the solar cell becomes maximum. Since the output of the inverter is connected to the power system, its output voltage is equal to the system. As a result, when the output power from the solar cell is less than the power consumption at the load, the insufficient power is supplemented by the power system, and when the output power is larger than the power consumption, surplus power is supplied to the power system. Thus, a stable power supply to the load can be performed while extracting the maximum output from the solar cell.

On the other hand, when the power system is cut off and the self-sustaining operation is performed, the first DC / DC converter determines the input so as to maximize the solar cell output as in the case of the cooperative operation. At this time, the second DC / DC converter is also operated, determines the input voltage of the inverter, and supplies the power from the storage battery to the inverter. Therefore, even during self-sustained operation, the solar cell is operated to have the maximum output, and the power generation capacity can be fully utilized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of a photovoltaic power generation system including a power conditioner 11 according to the present embodiment. The power conditioner 11 includes a boost chopper 12 corresponding to a first DC / DC converter, an inverter 13, a bidirectional chopper 14 corresponding to a second DC / DC converter, and a power failure detection circuit 15. .

The boost chopper 12 includes a current / voltage sensor 12A on an input line from the solar cell 20, and receives a signal from the current / voltage sensor 12A to control a switching element of the boost chopper 12. The control circuit 12B is provided, and can control the operation of the switching element so that the product of the current and the voltage from the solar cell 20 is maximized.

On the other hand, the inverter 13 is connected to the step-up chopper 12
Is converted into AC power. Inverter 13
The power line L connected to the power system 22 (for example, a commercial power supply of 200 V AC) via a switch (not shown)
1 and a power line L2 connected to the independent load 24. The power failure detection circuit 15 is configured to detect, for example, the voltage of the power line L1 and detect the power failure state of the power system 22 based on the voltage.

The bidirectional chopper 14 outputs the output from the storage battery 21 to the storage battery 21 by increasing or decreasing the power on the input side of the inverter, and starts operating when a detection signal from the power failure detection circuit 15 is received. Then, the DC power from the storage battery 21 is controlled to be constant.

Next, the operation of the power conditioner 11 according to this embodiment will be described. <At the time of interconnection operation> The DC output from the solar cell 20 is boosted to a DC voltage of, for example, 300 V DC by the boosting chopper 12, converted to AC power of 200 V AC (effective value) by the inverter 13, and transmitted via the power line L 1. AC power is supplied to the load 23 in cooperation with the power system 22. At this time, if the output power of the solar cell 20 is smaller than the power consumption of the load 23, the shortfall is
Supplemented by. On the other hand, when the output power from the solar cell 20 is larger than the power consumption of the load 23,
Surplus power flows backward.

Here, the step-up chopper 12 is
Is operated by the maximum power follow-up control so that the output power from the power supply becomes maximum. The output of the inverter 13 is the power system 2
2, the output voltage becomes equal to the system 22. At this time, the operation of the bidirectional chopper 14 is stopped, and the occurrence of unnecessary loss is suppressed.

<At the time of self-sustaining operation> On the other hand, when the power failure detection circuit 15 detects a power failure state of the power system 22, a detection signal is output from the power failure detection circuit 15 and the control circuit starts the operation of the bidirectional chopper 14. At the same time, the output side of the inverter 13 is connected via a power line L2 to, for example, a self-standing load 24 having a load voltage of 100V. Thus, when the output power from the solar cell 20 is smaller than the power consumption of the self-contained load 24, the shortage is supplemented by the storage battery 21. When the output power is large, surplus power is charged to the storage battery 21 so-called self-sustaining operation. Will be

Here, in the present embodiment, the output power of the storage battery 21 is provided to the input side of the inverter 13 via the bidirectional chopper 14. Therefore, unlike the conventional configuration, the output voltage Vout from the solar cell 20 is not dominated by the output voltage Vb of the storage battery 21.
It is possible to extract the maximum power Pmax from the solar cell 20 as in the case of the above-described interconnection operation. In addition, the storage battery 21
Is supplied to the inverter 13 side via the bidirectional chopper 14, and controls the output voltage of the bidirectional chopper 14 to be a constant value equal to or higher than the peak value of the output voltage of the inverter 13. Therefore, since the input voltage of the inverter 13 is always kept constant, the input voltage of the step-up chopper 12, that is, the output voltage of the solar cell 20 is controlled by the control circuit 1
2B can be controlled freely, and eventually, as in the case of the linked operation, the boost chopper 12 can be controlled to follow the maximum power so that the output power from the solar cell 20 is maximized.

<Other Embodiments> The present invention is not limited to the above embodiments. For example, the following embodiments are also included in the technical scope of the present invention.
In addition to the following, various changes can be made without departing from the scope of the invention.

(1) In the above embodiment, the power conditioner constituting the photovoltaic power generation system has been described. However, the present invention is not limited to this. For example, the step-up chopper 12, the inverter 13, the bidirectional chopper 14, and the control thereof And a power outage detection circuit 15 that constantly supplies power to the load together with the storage battery without being connected to the power system (corresponding to the invention of claim 1). Do).

(2) In the above embodiment, the first DC / D
Although the step-up chopper 12 has been described as an example of the C converter, any converter that converts an arbitrary output voltage Vm corresponding to the maximum power Pmax from the solar cell 20 to a predetermined DC voltage and outputs the converted DC voltage may be used. It may be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solar power generation system including a power conditioner according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional solar power generation system including a power conditioner.

FIG. 3 is a graph showing the relationship between the characteristics and output of a solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Power conditioner 12 ... Step-up chopper (1st DC / DC converter) 13 ... Inverter 14 ... Bidirectional chopper (2nd DC / DC converter) 15 ... Power failure detection circuit 20 ... Solar cell 21 ... Storage battery 22 ... Electric power System 23 ... Load 24 ... Independent load

Continued on the front page (72) Inventor Takashi Takuma 1-term, Kinosho-in, Nishino-sho, Ino-Babacho, Minami-ku, Kyoto F-term in Nippon Battery Co., Ltd. 5G066 HA30 HB06 HB09 JA02 JA07 JB03 5H007 AA12 BB05 BB07 CB00 CC03 CC12 DA05 DA06 DC02 DC04 DC05 5H420 BB12 BB13 CC03 CC06 DD03 EB16 EB37 EB39 FF03 FF04 LL03

Claims (2)

[Claims] 1. A first DC / DC converter which operates at an input voltage at which output power from a solar cell is maximized to convert a voltage, and converts DC power from the first DC / DC converter into AC power An inverter for converting the DC power from a storage battery charged by a charging device and supplying the DC power from the storage battery to the first DC / DC on the input side of the inverter;
A power conditioner for photovoltaic power generation, comprising: a second DC / DC converter that converts a predetermined DC voltage to an output of a converter and outputs the DC voltage. 2. A first DC / DC converter for converting a voltage by operating at an input voltage at which output power from a solar cell is maximum, and converting DC power from the first DC / DC converter into AC power An inverter for converting the DC power from a storage battery charged by a charging device and supplying the DC power from the storage battery to the first DC / DC on the input side of the inverter;
A second DC / DC converter that converts a predetermined DC voltage to an output side of the converter and outputs the DC voltage, a power failure detection circuit that detects a power failure in the power system, and the first and second DC / DCs.
A control unit for controlling the converter and the inverter, wherein the control unit is connected to the power system and always supplies power to a load connected to the power system. An interconnection operation for controlling the inverter and stopping the second DC / DC converter is performed, and when receiving a power failure detection signal that detects a power failure of the power system from the power failure detection circuit, the two DC / DC converters and A power conditioner for photovoltaic power generation, wherein an inverter is operated to control an output voltage of the second DC / DC converter to be an input voltage necessary for the inverter.